The present invention relates to medical infusion devices, and more particularly, to an improved combination continuous dose and bolus dose infusion system for delivering patient selectable controlled doses of intravenous drugs at controlled intervals above a controlled rate.
It is often necessary to intravenously supply patients with doses of pharmaceutically active liquids over a long period of time at a controlled rate. It is desirable that this be accomplished while the patient is in an ambulatory state.
The administration of effective doses of analgesics is highly subjective and depends on such factors as age, pain tolerance, renal function and other medications. For this reason, it is desirable that the patient have a certain amount of control over the dosage. However, it is also desirable that overdose be prevented. Many devices have been available in the past for allowing the self administration of analgesics. However, these have many drawbacks, including being bulky, complicated and expensive. Most of such devices also provide only an on demand rush of the drug.
One prior art infusion apparatus having many desirable characteristics is disclosed in U.S. Pat. No. 5,011,477, issued Apr. 30, 1991, to Winchell et al. This apparatus provides a combination of a continuous dose and a patient controlled bolus dose The device has the drawback of being complicated and expensive to manufacture.
Accordingly, it would be desirable to provide an improved low cost patient controlled analgesic infusion system for delivering intravenous drugs in a continuous background dosage, with the ability for patient selection of a bolus dose substantially on demand.